When i merge a record, i want to store the Id of the loosing/deleted record on the Merged/Winning record.

So I came across this documentation
https://www.salesforce.com/us/developer/docs/apexcode/Content/apex_triggers_merge_statements.htm

The following is the order of events when a merge occurs:

1.  The before delete trigger fires.
2.  The system deletes the necessary records due to the merge, assigns new parent records to the child records, and sets the MasterRecordId field on the deleted records.
3.  The after delete trigger fires.
4.  The system does the specific updates required for the master record. Normal update triggers apply.

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I created a custom field (text) on Contact and tried to put a after delete trigger like this

trigger RestoreMergedRecordInformation_Contact on Contact (after delete)
{
   
    Map<Id,String> mapMergeContacts = New Map<Id,String>();
    for(Contact delCon : Trigger.Old)
    {
        String oldString = mapMergeContacts.get(delCon.MasterRecordId);
        if(oldString != NULL)
        {
            oldString = oldString + String.valueOf(delCon.Id) + ';';
            mapMergeContacts.put(delCon.MasterRecordId,oldString);
        }
        else
        {
            mapMergeContacts.put(delCon.MasterRecordId,String.valueOf(delCon.Id) + ';');
        }
    }
   
    Set<Id> masterContactSet = New Set<Id>();
    masterContactSet = mapMergeContacts.keySet();
   
    List<Contact> masterContacts = [Select Id, Merged_Contacts__c from Contact Where Id in :masterContactSet];
    for(Contact thisCon : masterContacts)
    {
        thisCon.Merged_Contacts__c = mapMergeContacts.get(thisCon.Id);
        System.Debug('Id is - ' + thisCon.Id);
        System.Debug('Merged Contacts ' + mapMergeContacts.get(thisCon.Id));
    }
   
    update masterContacts;
}

Now I see I am getting an error since the winning record is being update ... error reads
"Apex trigger RestoreMergedRecordInformation_Contact caused an unexpected exception, contact your administrator: RestoreMergedRecordInformation_Contact: execution of AfterDelete caused by: System.DmlException: Update failed. First exception on row 0 with id 003xxxxxxxxxxxx; first error: SELF_REFERENCE_FROM_TRIGGER, Object 003xxxxxxxxxx is currently in a merge operation, therefore a trigger can not update it.: []: Trigger.RestoreMergedRecordInformation_Contact: line 56, column 1"

Experts, can you suggest if the trigger is being put on a wrong event (after delete).
Any suggestions?